A report prepared for the council's assets and services meeting last week said the sheep pavilion was officially opened in 1923, and the structure had remained largely unchanged since.
However, some pens had been removed to allow for wet weather access to the farmer's market, the report said.
In 1974, the pens were sold to the Marlborough District Council but remained under the management of the Marlborough A&P Association. They became heritage listed in 1985.
As part of the conditions to remove the grandstand, the council also engaged with a heritage consultant to prepare a conservation plan for the sheep pavilion, which was completed in 2020.
The plan enabled the restoration work and improvements to be completed.
The report said losing the sheep pens would be "significant" to the historic landscape in Marlborough, and that there was an opportunity to support the long-term survival of the building through the work.
Speaking at the meeting through Zoom, council parks and open spaces manager Robert Hutchinson said it was important to give the pavilion a good celebration for its 100th anniversary, by starting to undertake the restoration work.
Hutchinson said architects had identified issues with the building, including significant works to the roof structure and beams.
He also showed councillors images of rot in the beams, telling them the structure of the building was "compromised". Sections of the gutter also needed to be replaced to take water away from the roof trusses.
Blenheim ward councillor David Croad asked Hutchinson if the repairs were all that would be needed.
Hutchinson said the repair work was from the surveyors' report, and there may be surprises.
"We don't know what those costs will be, we don't know what those repairs will be, we'll just have to deal with them at the time," Hutchinson said.
"Long-term there is a budget ... to deal with maintenance issues in the future."
Wairau-Awatere councillor Cynthia Brooks said pens were a "precious building".
"The architecture in it is beautiful, and you don't find many old wooden buildings still around.
"So I certainly support retaining it and bringing it back, if you like, and keeping it safe for the future."
A&P Association Marlborough president William Harris told councillors they planned to do some fundraising to meet the other half of the costs.
Details were being finalised, but it could include members of the public sponsoring a sheet of iron. The total quoted cost of repairs was $127,500.
The association had lost some funding because they had not been able to have two A&P shows due to Covid-19.
The committee approved the funding, subject to full council approval this month.
